1 /* tnum: tracked (or tristate) numbers
2 *
3 * A tnum tracks knowledge about the bits of a value. Each bit can be either
4 * known (0 or 1), or unknown (x). Arithmetic operations on tnums will
5 * propagate the unknown bits such that the tnum result represents all the
6 * possible results for possible values of the operands.
7 */
8
9 #ifndef _LINUX_TNUM_H
10 #define _LINUX_TNUM_H
11
12 #include <linux/types.h>
13
14 struct tnum {
15 u64 value;
16 u64 mask;
17 };
18
19 /* Constructors */
20 /* Represent a known constant as a tnum. */
21 struct tnum tnum_const(u64 value);
22 /* A completely unknown value */
23 extern const struct tnum tnum_unknown;
24 /* A value that's unknown except that @min <= value <= @max */
25 struct tnum tnum_range(u64 min, u64 max);
26
27 /* Arithmetic and logical ops */
28 /* Shift a tnum left (by a fixed shift) */
29 struct tnum tnum_lshift(struct tnum a, u8 shift);
30 /* Shift (rsh) a tnum right (by a fixed shift) */
31 struct tnum tnum_rshift(struct tnum a, u8 shift);
32 /* Shift (arsh) a tnum right (by a fixed min_shift) */
33 struct tnum tnum_arshift(struct tnum a, u8 min_shift, u8 insn_bitness);
34 /* Add two tnums, return @a + @b */
35 struct tnum tnum_add(struct tnum a, struct tnum b);
36 /* Subtract two tnums, return @a - @b */
37 struct tnum tnum_sub(struct tnum a, struct tnum b);
38 /* Bitwise-AND, return @a & @b */
39 struct tnum tnum_and(struct tnum a, struct tnum b);
40 /* Bitwise-OR, return @a | @b */
41 struct tnum tnum_or(struct tnum a, struct tnum b);
42 /* Bitwise-XOR, return @a ^ @b */
43 struct tnum tnum_xor(struct tnum a, struct tnum b);
44 /* Multiply two tnums, return @a * @b */
45 struct tnum tnum_mul(struct tnum a, struct tnum b);
46
47 /* Return a tnum representing numbers satisfying both @a and @b */
48 struct tnum tnum_intersect(struct tnum a, struct tnum b);
49
50 /* Return @a with all but the lowest @size bytes cleared */
51 struct tnum tnum_cast(struct tnum a, u8 size);
52
53 /* Returns true if @a is a known constant */
54 static inline bool tnum_is_const(struct tnum a)
55 {
56 return !a.mask;
57 }
58
59 /* Returns true if @a == tnum_const(@b) */
60 static inline bool tnum_equals_const(struct tnum a, u64 b)
61 {
62 return tnum_is_const(a) && a.value == b;
63 }
64
65 /* Returns true if @a is completely unknown */
66 static inline bool tnum_is_unknown(struct tnum a)
67 {
68 return !~a.mask;
69 }
70
71 /* Returns true if @a is known to be a multiple of @size.
72 * @size must be a power of two.
73 */
74 bool tnum_is_aligned(struct tnum a, u64 size);
75
76 /* Returns true if @b represents a subset of @a. */
77 bool tnum_in(struct tnum a, struct tnum b);
78
79 /* Formatting functions. These have snprintf-like semantics: they will write
80 * up to @size bytes (including the terminating NUL byte), and return the number
81 * of bytes (excluding the terminating NUL) which would have been written had
82 * sufficient space been available. (Thus tnum_sbin always returns 64.)
83 */
84 /* Format a tnum as a pair of hex numbers (value; mask) */
85 int tnum_strn(char *str, size_t size, struct tnum a);
86 /* Format a tnum as tristate binary expansion */
87 int tnum_sbin(char *str, size_t size, struct tnum a);
88
89 #endif /* _LINUX_TNUM_H */